Following on the announcement last week that they would offer Virtual Private Cloud (VPC) instances for the peace of mind of enterprise customers, Amazon today introduces an additional security feature to their web services portfolio: multi-factor authentication.

Unlike the VPC service, which has some rough analogs elsewhere in cloud-land, I'm not aware of any other cloud service provider offering fob-based multi-factor authentication for account access. However, like the VPC offering, I'm not sure this necessarily assuages the core doubts surrounding cloud computing security, namely that the walls behind the doors may not be as strong as one would like. This feature certainly improves the lock on the door; depending on the extent of the internal security features, it may also improve the strength of the walls, but that isn't something that Amazon, or any other provider, have been eager to disclose any details on as of yet.